Villain-unknown.I obviously defend my blind aggressively with a 3bet.I dont know what he would raise on this relatively dry board with.May be AQ that wants to protect from the FD.I see no other option but b/f.Other options?

I think it is mostly bluff or some kind of draw but if you´re not sure that players would not raise flop for value KQ, then I like your b/f
If you know we would not raise flop KQ or even AQ then it is easy shove, since you should be ahead most times and you sometimes take pot down also since he would bluffraise that spot